Comparison of characteristics of solar cells and LEDs

When comparing the characteristics of silicon crystal solar cells and LEDs, it can be found that they have many similarities as follows:

(1) All are semiconductor devices. Solar cells, like LEDs, are semiconductor devices, which are diodes made of PN structure. It’s just that solar cells convert light into electrical energy, and LEDs convert electrical energy into light energy. The lighting system composed of them should be more meaningful “semiconductor green lighting”. The real green lighting system in the future should be: solar cells and LEDs, that is, PN junction + PN junction semiconductor green lighting system. It has the unmatched advantages of any lighting system in the world: clean, without any pollution, high efficiency and long life.

(2) Have the same temperature characteristics. Both solar cells and LEDs have negative temperature coefficients. When the temperature rises by 1°C, the voltage of the monolithic solar cells will drop by 2mV; for LED, the luminous flux decreases by half for every 10°C increase in temperature. When the temperature reaches 80°C, its luminous flux drops to 0. Similarly, at this temperature, the solar cell is close to not working.

(3) Have the same long service life. The service life of solar cell components is 25-30 years, which is the longest service life of various batteries and power generation devices. LED is the longest service life of various electric light sources. Even when working under harsh outdoor conditions, the life span is more than 50,000 hours, and the life span of power LEDs is expected to reach tens of thousands of hours. Therefore, in some occasions where maintenance and equipment replacement are difficult, the use of solar cells and LED light sources can significantly reduce the cost of installation and use.

(4) The packaging technology is very similar. Both solar cells and LEDs need to be packaged with materials with good light transmittance, UV resistance, and good sealing performance. Packaging technology determines the performance and life of solar cells and LEDs. Solar cell modules are sealed with flat glass and polymer materials, and some are directly packaged with polymer materials, and the entire system has no rotating parts. LED is a solid light source encapsulated with organic polymer materials. There are no easily damaged parts such as glass bulbs and filaments in its structure. It is an all-solid structure, so it can withstand vibrations and shocks and has a strong structure.

(5) Current and voltage characteristics are similar. Since solar cells, like LEDs, are semiconductor devices and are composed of PN junctions, the output characteristic curve of solar cells is very similar to the current and voltage characteristic curves of LEDs, and there is an obvious inflection point. For solar cells, this inflection point is the maximum output power point of the solar cell; for LEDs, this inflection point is its corresponding working voltage. If this voltage is exceeded, the LED will be overloaded and burned. The single voltage of the solar cell is 0.5~1.2V. Various DC voltage power supplies can be obtained through series and parallel connections. The LED drive also uses a DC power supply. The operating voltage of a single tube is generally between 0.8V and 3.8V, and it can also be used in series or parallel. The two are very compatible, which can save the need for inverters in ordinary solar photovoltaic lighting systems. This can improve energy efficiency, save costs, and improve system reliability.

(6) All face the same application development bottleneck. The bottleneck of the popularization of solar cells is mainly that the price is relatively high, and there are more technical problems with LEDs. The efficiency of the current commercial white LEDs needs to be further improved. According to the current LED technology development speed, some people predict that by 2015, the luminous efficiency of white LEDs may reach 150~200lm/W, which far exceeds the luminous efficiency of all current lighting sources. In addition, its color rendering is not good. Although its service life is longer than other light sources, it is still far from the life of 100000h.

(7) All are green products. Both of these products are green and environmentally friendly products. The high-efficiency electric light sources that can be seen at present basically contain rare earth materials, harmful gases or radioactive elements that pollute the environment. LEDs rarely have this problem. Solar cells are a kind of clean energy without any pollution to the environment, even the noise of wind power generation.

(8) The support of the control circuit is required in use. Just as the use of solar cells must have a controller or inverter, the use of LEDs must also have a constant current circuit. Without the support of the control circuit, neither the solar cell nor the LED can work normally.